Interest in organic electronics comes from the low cost of plastics, and the relative ease of organic compounds processing with most successful application in organic light-emitting devices (OLEDs), thin-film transistors (TFTs) and thin film organic photovoltaic cells. See, e.g., S. R. Forrest, The path to ubiquitous and low-cost organic electronic appliances on plastic, Nature, 428, 911-918 (2004); C. D. Sheraw et al., Organic thin-film transistor-driven polymer-dispersed liquid crystal displays on flexible polymeric substrates, Appl. Phys. Lett., 80(6), 1088-1090 (2002); D. R. Hines et al., Nanotransfer printing of organic and carbon nanotube thin-film transistors on plastic substrates, Appl. Phys. Lett., 86, 163101 (2005); and H. Hoppe et al., Organic solar cells: an overview, J. Mater. Res., 19(7), 1924-1945 (2004), the entire contents of each are incorporated herein by reference. Flexible electronic devices typically rely on the conducting properties of small molecules, conductive polymers and biological materials. However, their inherent low carrier mobilities (<1 cm2V−1 s−1), low electrical conductivity (σ˜10−6 S cm−1) and low charge carrier velocity (10 cm s1) represent serious limitation and underlines the need of perfect transparent conductor that will possess both the flexibility of organics and higher carrier mobilities. Graphene has emerged as this long sought conductor due to its zero-band gap, extremely high electron mobilities of 10,000-70,000 cm2V−1 s−1, and low absorption (2.3%) in the visible spectrum. See, e.g., W. Warta et al., Ultrapure, high mobility organic photoconductors, Appl. Phys. A, 36, 163-170 (1985); P. E. Burrows et al., Electroluminescence from trap-limited current transport in vacuum deposited organic light emitting devices, Appl. Phys. Lett., 64, 2285-2287 (1994); F. Schwierz, Graphene transistors, Nature Nanotechnol., 5, 487-496 (2010); and F. Bonaccorso et al., Graphene photonics and optoelectronics, Nature photonics, 4, 611-622 (2010), the entire contents of each are incorporated herein by reference. Successful graphene incorporation into plastics shows promise in the production of flexible touch screens, displays, smart windows as well as a viable replacement for ITO technology. See, e.g., J. K. Wassei et al., Graphene, a promising transparent conductor, Materials today, 13(3), 52-59 (2010); L. G. D. Arco et al., Continuous, highly flexible, and transparent graphene films by chemical vapor deposition for organic photovoltaics, ACS Nano, 4(5), 2865-2873 (2010); and P. Matyba et al., Graphene and mobile ions: the key to all-plastic, solution processed light-emitting devices, ACS Nano, 4(2), 637-642 (2010), the entire contents of each are incorporated herein by reference. However, a truly manufacturable process in any of the above mentioned applications requires controlled, uniform graphene growth and precise graphene placement on top of organic surfaces, along with the development of cost-effective techniques for organic device fabrication.
High-quality graphene is typically produced via thermal graphitization of SiC, or chemical vapor deposition (CVD) on metals substrates, with the latter showing the most promise for lower cost and scalability to large areas. See, e.g., X. Li et al., Large-area synthesis of high-quality and uniform graphene films on copper foils, Science, 324, 1312-1314 (2009) and S. Bae et al., Roll-to-roll production of 30-inch graphene films for transparent electrodes, Nature Nanotechnol., 5, 574-578 (2010), the entire contents of each is incorporated herein by reference. For device fabrication, graphene has to be transferred to semiconductor or plastic substrates. Typically, the graphene transfer procedure involves using a polymer mediator (PMMA or PDMS) to keep the graphene film intact and prevent folding while the Cu foil is chemically etched. The latter requires strong acids such as HNO3, which often produces hydrogen bubbles and damages the graphene. See, e.g., W. Regan et al., A direct transfer of large-area graphene, Appl. Phys. Lett., 96, 113102 (2010) and K. S. Kim et al., Large-scale pattern growth of graphene films for stretchable transparent electrodes, Nature, 457, 706-710 (2009), the entire contents of each is incorporated herein by reference. Aqueous iron chloride (FeCl3) has been explored as a mild alternative to acid etching, but the metal foil etching step is a hazardous and time consuming process that can take up to twelve hours to complete. See, e.g., V. P. Verma et al., Large-area graphene on polymer film for flexible and transparent anode in field emission device, Appl. Phys. Lett., 96, 203108 (2010), the entire contents of which are incorporated herein by reference. Extensive soaking of the graphene/PMMA stack in deionized water is needed for the removal of the etchant's residuals. This step may also take hours. After the metal foil is dissolved, the graphene/PMMA stack is placed onto an arbitrary surface and the polymer mediator is dissolved in acetone to yield “pristine” graphene on semiconductor or polymer substrate. The detrimental effect of the polymer solvent residues in graphene has been recognized and include introduction of variety of defects into the graphene layer. Thus, alternative approaches to the use of polymer substrate as a mediator mainly involving thermal release tape have been explored. See, e.g., J. D. Caldwell et al., Technique for the dry transfer of epitaxial graphene onto arbitrary substrates, ACS Nano, 4(2), 1108-1114 (2010); Y. Lee et al., Wafer-scale synthesis and transfer of graphene films, Nano Lett., 10, 490-493 (2010); and L. Song et al., Transfer printing of graphene using gold film, ACS Nano, 3(6), 1353-1356 (2009), the entire contents of each are incorporated herein by reference. As an example, the protocol used by Bae et al. involves placing tape/graphene/Cu stack between two rollers at 0.2 MPa pressure, then the Cu foil is chemically etched. The Gr/tape stack is washed with diionized water and placed on target substrate. Gr/tape/substrate is exposed to mild heat (90-120° C.) to remove tape residues. While the protocol for transfer varies between research groups, the metal foils are always chemically etched, which is time consuming, the graphene film is altered by the exposure to chemicals, the metal substrates are destroyed and hazardous chemical waste is generated—none of which is desirable for a large scale device production.